(CNN) - The father of George Zimmerman, the man accused of shooting and killing an unarmed black teen in Florida, says the 17-year-old threatened to kill Zimmerman and then beat him so badly that it forced Zimmerman to shoot him.

"Trayvon Martin said something to the effect of, 'You're going to die now' or 'You're going to die tonight,' something to that effect," Robert Zimmerman told Orlando TV station WOFL. "He continued to beat George. At some point, George pulled his pistol. Did what he did."

A surveillance video from the Sanford police headquarters the night of the incident raises questions about the description of a beating.

It shows Zimmerman, his hands cuffed, exiting a patrol car and being led into the police station. First broadcast Wednesday by ABCNews.com, the video does not provide close-ups, but also does not show clear signs of Zimmerman having injuries.

Joe Oliver, a friend of Zimmerman's, said Zimmerman told him he was "cleaned up by cops at the scene" that night before being taken to the station.

Oliver also said it was discovered the next day that Zimmerman's nose was broken.

Craig Sonner, George Zimmerman's attorney, said Thursday the video does not support or contradict Robert Zimmerman's description. It is "very grainy," he said on NBC's "Today" show. Sonner also noted that the injuries Zimmerman sustained were "later cleaned up."

A police report says Zimmerman was bleeding from the nose and the back of his head when police arrived at the scene of the killing February 26. He was given first aid in the police car, the report says.